Medical Policy

Subject: Continuous Monitoring of Intraocular Pressure
Document #: MED.00118 Current Effective Date:    06/28/2017
Status: Reviewed Last Review Date:    05/04/2017


This document addresses the continuous monitoring of intraocular pressure (IOP).

Increased IOP is associated with a greater risk of developing glaucoma and disease progression, although glaucoma may occur with normal IOP.  There are two major types of glaucoma; open-angle and closed-angle.  Open-angle glaucoma is a chronic condition that progresses slowly over a long period of time.  It is the most common type of glaucoma.  Closed-angle glaucoma quickly develops and can cause painful and immediate vision problems.  

Changes in IOP occur normally over the course of a day, with peaks in pressure reached during the night.  It has been postulated that fluctuations in intra-ocular pressure are associated with the progression of glaucoma.  Measurement of IOP can help lead to a diagnosis of glaucoma.  However, the most commonly used tests for glaucoma (tonometry, ophthalmoscopy, perimetry, and gonioscopy) are limited to single snapshots in time.  Researchers are exploring the use of 24-hour monitoring of IOP as a means to measure fluctuations in IOP in order to assess and monitor treatment for glaucoma.   

Position Statement

Investigational and Not Medically Necessary:

The use of continuous monitoring of intraocular pressure is considered investigational and not medically necessary for all indications.


Continuous, non-invasive measurement of IOP is being explored as a means to diagnose and manage elevated IOP.  In a 2011 study by Mansouri and colleagues, the authors report on 15 participants with open-angle glaucoma who wore a disposable silicone contact lens with an embedded micro-electromechanical system to measure continuous IOP.  A total of 13 participants completed the 24-hour study monitoring period.  Discontinuation of the device was due to device intolerance and technical device malfunction.  Of the 13 participants who completed the monitoring period, 9 of them had the highest signals recorded during the nocturnal period.  No serious side effects were reported.

Pajic and colleagues (2011) conducted a study using a disposable silicone contact lens embedded with a micro-electromechanical system to measure continuous IOP in 5 individuals with chronic open-angle glaucoma and normal IOP.  IOP measurements were obtained before and after treatment with an intraocular pressure-lowering drug.  Continuous 24-hour IOP fluctuation monitoring was performed on two occasions separated by at least 6 weeks in each participant.  In the control session, participants were untreated or previous IOP-lowering medication was washed-out for a minimum of 6 weeks.  In the treatment session, participants received IOP-lowering medication for at least 6 weeks.  The continuous IOP recordings were analyzed for differences between daytime and nighttime data and for repeatability over time.  Additionally, profiles recorded for each participant in treated and non-treated conditions were compared.  The authors reported that the data recorded during daytime portions of the recordings showed higher coefficients of variation than nighttime data.  Positive and significant linear slopes for the transition period from wake time to sleep time were identified in all subjects in the absence of anti-glaucomatous treatment, while 3 of the 5 participants had no significant slopes detected under treated conditions.  The authors concluded that the continuous IOP fluctuation monitoring device is sensitive to individual IOP rhythms and to differences in such rhythms due to anti-glaucomatous drug therapy.

Mansouri and colleagues (2012) assessed the safety, tolerability, and reproducibility of IOP patterns during repeated continuous 24-hour IOP monitoring with a contact lens sensor (CLS).  A total of 40 subjects suspected of having glaucoma (n=21) or with established glaucoma (n=19) were included in the study.  There was moderate correlation between the two sessions, suggesting good reproducibility of the IOP recordings.  With regard to tolerability, there was no difference in adverse events or survey scores between those with established glaucoma compared with those with suspected glaucoma.  Main adverse events included blurred vision (82%), conjunctival hyperemia (80%), and superficial punctate keratitis (15%).  The researchers concluded that repeated use of the CLS demonstrated good safety and tolerability and that data from continuous 24-hour IOP monitoring may be useful in the management of individuals with glaucoma.  A limitation of this study is the absence of a control group within the cohort that was without glaucoma, which resulted in the study not addressing the reproducibility and accuracy of IOP measurements in populations with normal or near-normal IOP.

In a prospective, single-center, open, observational parallel study in 2013 by Lorenz and colleagues, a 24-hour IOP monitoring device was evaluated for safety and tolerability.  A total of 20 control participants were compared to 20 participants with glaucoma.  The soft disposable contact lens with telemetry chip and strain gauge sensor was placed in 1 eye for 24 hours.  Tolerability was measured using a visual analog scale.  The safety measures included best corrected visual acuity, pachymetry, epithelial defects, conjuctival erythema and corneal topography.  Of the 20 participants (in both control and observed group), 19 of them completed the 24-hour wearing period.  The early discontinuation was attributed to pain or inappropriate fitting of the sensor due to steep corneal radii.  Mean tolerability in the control group was 21.8 and 26.8 in the glaucoma group.  While both the control group and the glaucoma group had similar safety and tolerability, the population size in this study was small.

In a small study by Mottet and colleagues (2013), researchers evaluated 24-hour IOP rhythm reproducibility during repeated continuous 24-hour IOP monitoring with a CLS and noncontact tonometry (NCT) in 12 healthy participants from a single institution.  Participants received four 24-hour sessions of IOP measurements over a 6-month period.  After initial randomized attribution, the IOP of the first eye was measured hourly using NCT and the contralateral eye was measured continuously using a contact lens sensor:  Two sessions with NCT measurements in one eye and continuous contact lens measurements in the fellow eye, one session with continuous contact lens sensor measurements in only one eye, and one session with NCT measurements in both eyes were conducted.  The authors concluded that continuous IOP using a CLS is an accurate and reproducible method to characterize the nyctohemeral IOP rhythm in healthy participants but does not allow for estimating the IOP value in millimeters of mercury corresponding to the relative variation of the electrical signal measured.

In 2014, Hollo and colleagues reported the results of a trial which evaluated 24-hour continuous IOP monitoring with a telemetric contact lens sensor (CLS) to detect prostaglandin-induced IOP reduction.  A total of 9 individuals with ocular hypertensive and primary open-angle glaucoma were washed out from IOP-lowering medication for 6 weeks.  One study eye per participant underwent 3 baseline 24-hour measurement curves 4 days apart: 2 curves employing continuous monitoring with a CLS and 1 curve using Goldmann applanation tonometry (GAT).  Subsequently, the participants underwent travoprost monotherapy for a total of 3 months.  Continuous IOP pressure monitoring using the CLS and GAT curves were repeated on the study eyes under treatment at the end of the third month.  The 24-hour GAT IOP (mean ± SD) diminished from 22.91 ± 5.11 to 18.24 ± 2.49 mmHg (p<0.001).  In contrast, the means of the 3 contact lens sensor curves demonstrated no significant difference (152.94, 142.35, and 132.98 au, p=0.273).  The authors concluded that the continuous monitoring of IOP utilizing the CLS cannot be clinically used to monitor changes in IOP induced by topical medication in glaucoma, and has limited value in identification of transient IOP elevation periods.

Agnifili and colleagues (2015) conducted an observational, nonrandomized study which explored the circadian IOP patterns in healthy subjects, in primary open angle and normal tension glaucoma (POAG; NTG) using a CLS.  A total of 10 healthy participants (Group 1, 10 eyes) and 20 individuals with glaucoma [20 eyes, 10 with POAG (Group 2) and 10 with NTG (Group 3)] were enrolled.  All of the participants were controlled with prostaglandin analogues.  The primary outcome was the 24-hour IOP pattern.  Secondary outcomes included the morning (6AM-11AM), afternoon/evening (noon-11PM) and night (midnight-5AM) subperiod patterns, peaks and prolonged peaks (>1 hour).  Mean 24-hour IOP pattern reflected a nocturnal acrophase in all groups.  Patterns were significantly different among groups (p=0.02), with highest nocturnal IOP values occurring in the POAG group.  Prolonged peaks were more common in subjects with glaucoma (70%) than in healthy participants (33.3%) (p<0.001).  Significant differences were identified for Groups 2 and 3 in the morning versus afternoon/evening (p=0.019 and p=0.035, Bonferroni correction), morning versus night (p=0.005 and p<0.0001) and afternoon/evening versus night periods comparisons (p<0.0001 for both groups).  In Group 1, patterns differed significantly in the morning versus night and afternoon/evening versus night period comparisons (p<0.0001).  The authors concluded that continuous IOP monitoring with the CLS demonstrated a nocturnal acrophase in healthy participants and, more markedly, in glaucoma.  Because the diurnal IOP profile seems not to predict the nocturnal rhythm, the circadian IOP pattern should be assessed in clinical practice.

Overall, continuous IOP monitoring with a CLS and standard tonometry for measurement of IOP are two methods that are not directly comparable and do not have the same objective.  In contrast to tonometry, which indirectly measures the IOP by applying a force on the cornea, the CLS monitors IOP indirectly via the ocular volume at the corneoscleral area.  The exact calibration of the CLS output to mmHg is complex and cannot easily be translated to the mmHg of pressure expressed in tonometry. 

A 2012 technology brief funded by the National Institute for Health Research (NIHR) which focused on the SENSIMED Triggerfish® device concluded that:

Further research into the relationship between fluctuations in intraocular pressure and the glaucoma disease process is needed. The need for further studies investigating the reproducibility and accuracy of the Sensimed Triggerfish® measurements in a large number of patients has also been suggested.

No published clinical studies were identified which compared the rates of glaucoma progression in individuals who underwent continuous monitoring of IOP with individuals who are monitored using current standard practice.  Also, the peer-reviewed studies consist of small study populations and lack long-term follow-up. 

In March 2016, the SENSIMED Triggerfish CLS received FDA marketing clearance for the following use:

To detect the peak patterns of variation in intraocular pressure over a maximum period of 24 hours to identify the window of time to measure intraocular pressure by conventional clinical methods. The SENSIMED Triggerfish® is indicated for patients 22 years of age and older (FDA, 2017).


In healthy individuals, IOP is generally between 10 and 20 mmHg.  Small changes in the IOP during the course of the day and from one season to another are normal.  IOP varies with changes in respiration or heart rate, and may also be affected by fluid intake and exercise.  Temporary changes in IOP may also be caused by coughing, vomiting, or straining to lift heavy objects.  Significant and/or persistent changes in IOP may be caused by anatomical problems (such as excessive production or drainage of aqueous fluid), inflammation in the eye following trauma or infection, medication use and genetic factors.  A significant change in IOP that is sustained and goes untreated may eventually cause vision problems and lead to eye disease.

Glaucoma is a grouping of diseases that can damage the optic nerve and result in vision loss and blindness.  Older adults have the greatest risk for developing glaucoma.  Glaucoma may occur when the normal pressure of the fluid inside the eye slowly rises. However, it can also occur in individuals who do not have a rise in eye pressure.

There are two major types of glaucoma; open-angle and closed-angle.  Open-angle glaucoma is a chronic condition that progresses slowly over a long period of time.  It is the most common type of glaucoma, affecting approximately 2.5 million Americans and is a leading cause of blindness.  Closed-angle glaucoma quickly develops and can cause painful and immediate vision problems.  Closed-angle glaucoma is less common than open-angle glaucoma.

Measurement of IOP can help lead to a diagnosis of and manage treatment for glaucoma.  The use of 24-hour monitoring of IOP is being explored as a means to continuously measure variations in the IOP.

According to the manufacturer's website, the SENSIMED Triggerfish device consists of a disposable soft silicone contact lens which contains a sensor, a flexible disposable self-adhesive antenna placed around the eye and a pocket-sized recorder.  The recorder sends the collected information to a doctor's computer via Bluetooth.  The CLS measures small changes in the curvature of the cornea which are purported to reflect changes in the IOP.


Glaucoma: A grouping of diseases that can damage the optic nerve and result in vision loss and blindness. 

Intraocular: Located within or administered through the eye.

Intraocular pressure (IOP): The tissue pressure within the eye; a measurement of the balance between the production and drainage of aqueous humor.

Optic nerve: A collection of more than 1 million nerve fibers which connects the retina to the brain.

Retina: The light-sensitive tissue at the rear of the eye.


The following codes for treatments and procedures applicable to this document are included below for informational purposes. Inclusion or exclusion of a procedure, diagnosis or device code(s) does not constitute or imply member coverage or provider reimbursement policy. Please refer to the member's contract benefits in effect at the time of service to determine coverage or non-coverage of these services as it applies to an individual member.

When services are Investigational and Not Medically Necessary:
For the following procedure code; or when the code describes a procedure indicated in the Position Statement section as investigational and not medically necessary.

0329T Monitoring of intraocular pressure for 24 hours or longer, unilateral or bilateral, with interpretation and report
ICD-10 Diagnosis  
  All diagnoses

Peer Reviewed Publications:

  1. Agnifili L, Mastropasqua R, Frezzotti P, et al. Circadian intraocular pressure patterns in healthy subjects, primary open angle and normal tension glaucoma patients with a contact lens sensor. Acta Ophthalmol. 2015; 93(1):e14-e21.
  2. Hollo G, Kothy P, Vargha P. Evaluation of continuous 24-hour intraocular pressure monitoring for assessment of prostaglandin-induced pressure reduction in glaucoma. J Glaucoma. 2014; 23(1):e6-e12.
  3. Lorenz K, Korb C, Herzog N, et al. Tolerability of 24-hour intraocular pressure monitoring of a pressure-sensitive contact lens. J Glaucoma. 2013; 22(4):311-316.
  4. Mansouri K, Medeiros FA, Tafreshi A, Weinreb RN. Continuous 24-hour monitoring of intraocular pressure patterns with a contact lens sensor: safety, tolerability, and reproducibility in patients with glaucoma. Arch Ophthalmol. 2012; 130(12):1534-1539.
  5. Mansouri K, Shaarawy T. Continuous intraocular pressure monitoring with a wireless ocular telemetry sensor: initial clinical experience in patients with open angle glaucoma. Br J Ophthalmol. 2011; 95(5):627-629.
  6. Mottet B, Aptel F, Romanet JP, et al. 24-hour intraocular pressure rhythm in young healthy subjects evaluated with continuous monitoring using a contact lens sensor. JAMA Ophthalmol. 2013; 131(12):1507-1516.
  7. Pajic B, Pajic-Eggspuchler B, Haefliger I, et al. Continuous IOP fluctuation recording in normal tension glaucoma patients. Current Eye Research 2011; 36(12):1129-1138.

Government Agency, Medical Society, and Other Authoritative Publications:

  1. National Institute for Health Research (NHS). NIHR Horizon Scanning Centre. Sensimed Triggerfish® for 24-hour monitoring of changes in intraocular pressure in glaucoma. August 2012.
  2. U.S Food and Drug Administration. De Novo Classification Request for Sensimed Triggerfish®. February 2017. Available at: Accessed on February 22, 2017.
Websites for Additional Information
  1. American Optometric Association. Glaucoma. Available at: Accessed on February 22, 2017.
  2. National Eye Institute. Facts About Glaucoma. Available at: . Accessed on February 22, 2017.

Intracoular Pressure Monitoring
SENSIMED Triggerfish

The use of specific product names is illustrative only. It is not intended to be a recommendation of one product over another, and is not intended to represent a complete listing of all products available.

Document History
Status Date Action
Reveiwed 05/04/2017 Medical Policy & Technology Assessment Committee (MPTAC) review. Updated Rationale, Background/Overview and References sections.
Reviewed 05/05/2016 MPTAC review. Updated Rationale and References sections. Removed ICD-9 codes from Coding section.
New 05/07/2015 MPTAC review. Initial document development.